64 Prof. Thomson, On the Carriers of the Positive Charges, etc. 



On the Carriers of the Positive Charges of Electr-icity emitted 

 by hot wires. By Sir J. J. THOMSON, M.A., F.R.S., Cavendish 

 Professor of Experimental Physics. 



[Read 9 November 1908.] 



A series of measurements of the values of e]m for the posi- 

 tively electrified particles given out by a strip of platinum wire 

 heated to incandescence were made by the method described by 

 the author in a paper on 'Positive Rays of Electricity,' Phil. Mag. 

 Oct. 1908. When the platinum had been kept for several days in 

 a high vacuum and heated repeatedly to incandescence, the value 

 of ejm for the great majority of the positively charged particles 

 was about 10727, showing that the mass of the particles was 

 about 27 times the mass of an atom of hydrogen. The masses 

 of molecules of CO and N^ are 28 times that of an atom of 

 hydrogen, and these molecules could not be distinguished by 

 determinations of ejm. The spectroscopic examination of the gas 

 given off by the hot wire after prolonged heating showed that the 

 CO spectrum was bright while that of nitrogen could not be 

 detected. For this reason I think the carriers of the positive 

 electricity are molecules of CO and not N2. 



After the platinum by long continued heating had been 

 brought into a state when the carriers had for the most part the 

 mass of a molecule of CO, hydrogen was let into the vessel and 

 the platinum foil made red-hot in an atmosphere of hydrogen, the 

 hydrogen was then pumped out ; determinations of e/m after this 

 process had been gone through showed that the average mass of 

 the carriers was only 8 or 9 times that of the hydrogen atom, 

 thus the absorption of the light gas by the platinum had 

 diminished the average weight of the carriers to about one-third 

 of its original value ; this I think shows that the carriers of the 

 positive electricity given out by hot metals are for the most part 

 the molecules of gas absorbed by the metal. I have much 

 pleasure in thanking Mr G. W. C. Kaye for the assistance he has 

 given me in making these experiments. 



